From: Jakub Kicinski <kuba@kernel.org>
To: Petr Machata <petrm@nvidia.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
<netdev@vger.kernel.org>, Ido Schimmel <idosch@nvidia.com>,
Kuniyuki Iwashima <kuniyu@google.com>,
Breno Leitao <leitao@debian.org>,
Andy Roulin <aroulin@nvidia.com>,
"Francesco Ruggeri" <fruggeri@arista.com>,
Stephen Hemminger <stephen@networkplumber.org>,
<mlxsw@nvidia.com>
Subject: Re: [PATCH net-next v2 6/8] net: core: neighbour: Reorder netlink & internal notification
Date: Sun, 25 Jan 2026 14:59:22 -0800 [thread overview]
Message-ID: <20260125145922.36ba88ad@kernel.org> (raw)
In-Reply-To: <f3ef74d5460f14c4d102b8a5857d4a6624da9a5a.1769012464.git.petrm@nvidia.com>
On Wed, 21 Jan 2026 17:43:40 +0100 Petr Machata wrote:
> The netlink message needs to be send inside the critical section where the
> neighbor is changed, so that it reflects the notified-upon neighbor state.
> On the other hand, there is no such need in case of notifier chain: the
> listeners do not assume lock, and often in fact just schedule a delayed
> work to act on the neighbor later. At least one in fact also takes the
> neighbor lock.
>
> This requires that the netlink notification be done before the internal
> notifier chain message is sent. That is safe to do, because the current
> listeners, as well as __neigh_notify(), only read the updated neighbor
> fields, and never modify them. (Apart from locking.)
Hopefully we're not setting a trap here that some driver will later
fall into.
next prev parent reply other threads:[~2026-01-25 22:59 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-21 16:43 [PATCH net-next v2 0/8] net: neighbour: Notify changes atomically Petr Machata
2026-01-21 16:43 ` [PATCH net-next v2 1/8] net: core: neighbour: Add a neigh_fill_info() helper for when lock not held Petr Machata
2026-01-21 16:43 ` [PATCH net-next v2 2/8] net: core: neighbour: Call __neigh_notify() under a lock Petr Machata
2026-01-21 16:43 ` [PATCH net-next v2 3/8] net: core: neighbour: Extract ARP queue processing to a helper function Petr Machata
2026-01-21 16:43 ` [PATCH net-next v2 4/8] net: core: neighbour: Process ARP queue later Petr Machata
2026-01-21 16:43 ` [PATCH net-next v2 5/8] net: core: neighbour: Inline neigh_update_notify() calls Petr Machata
2026-01-21 16:43 ` [PATCH net-next v2 6/8] net: core: neighbour: Reorder netlink & internal notification Petr Machata
2026-01-25 22:59 ` Jakub Kicinski [this message]
2026-01-21 16:43 ` [PATCH net-next v2 7/8] net: core: neighbour: Make one netlink notification atomically Petr Machata
2026-01-21 16:43 ` [PATCH net-next v2 8/8] net: core: neighbour: Make another " Petr Machata
2026-01-23 15:28 ` [PATCH net-next v2 0/8] net: neighbour: Notify changes atomically Simon Horman
2026-01-25 23:00 ` patchwork-bot+netdevbpf
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